Needing a seat that far forward is unusual. But I know form 1st hand experience that bikes can be set up to work very well that have to be modified with unusual gear to work. (I take production early '80s sport bikes, set them up fix gear with enormous stems and use them as very serviceable winter/rain/city bikes.)

I don't know your goals, nor your budget, but an approach that can be done is to go custom. I have had a local framebuilder make me two 160mm setback seatposts (as well as several of those stems). His approach is such that he could just as easily make a negative setback post at any setback you want. (He also uses Thompson 2-bolt clamps so you get a post that is a joy to set up.)

Go to the TiClycles website and take a look at some of the things they have done. (The post will cost you several hundred dollars.)

Ben